Means for protecting diaphragm controlled switches against excessive pressure



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OC- 27 1964 M. A. GILMAN MEANS FOR PROTECTING DIAPHRAGM CONTROLLEQ SWITCHES AGAINST EXCESSIVE PRESSURE Filed March 6. 1961 United States Patent C) 3,154,652 MEANS FOR PROTECTING DIAPHRAGM CON- TRULLED SWITCHES AGAINST EXCESSIVE PRESSURE Morris A. Gilman, 6510 N. Mozart St., Chicago 45, Ill. Filed Mar. 6, 1961, Ser. No. 117,762 8 Claims. (Cl. 20G-83) This invention relates to a liquid level control having a pressure sensitive diaphragm controlling the operation of the switch for turning the pump on and ofi.

Although diaphragm controlled switches are satisfactory where the rise in liquid level is within the limits that can be taken care of by the pump installation, it is necessary to provide a complete seal for the switch housing in order to protect the switch mechanism from water in installations subject to flood conditions. When the switch housing is completely sealed, variations in temperature and barometric pressure changes affect the activity of the switch.

In accordance with the present inveniion, I have adequately protected the switch mechanism against flood conditions in which the switch housing is completely covered, by means of an inverted, bonded sheath. The sheath prevents water from entering the switch compartment and provides an air buffer that not only protects the switch mechanism from the water, but also limits the strain to which the diaphragm will be subjected, regardless of the external pressure, by neutralizing the pressure at any desired level.

I have also increased the sensitivity of the switch control by providing an adjustment screw to accurately set the release holding force so that the switch operates at the exact point desired, with substantially no possibility of contact burn. The structure by means of which the above mentioned and other advantages of the invention are attained will be fully described in the following specication, taken in conjunction with the accompanying drawings showing a preferred illustrative embodiment of the invention, in which:

FIG. 1 is a side elevational view showing the liquid level control embodying the invention as applied to a pump seated on the bottom of a sump; and

FIG. 2 is an enlarged cross sectional view, showing the switch mechanism in open position.

Referring to the drawings, a pump is enclosed in a housing 2 located in a sump 3. A switch housing 4 is secured to the pump housing in any suitable manner, as, for example, by a clamp 5. Wiring 6 extends from the pump motor through a watertight fitting 7 in the top of the pump housing and is plugged into a coupler 8 that connects it in series to wiring 9 extending from the switch housing. A tubular breather duct 10 enclosing the wiring 9 extends upwardly from the switch housing to a point above the normal high water level of the sump. A sheath 11, secured to wiring 9 with a watertight seal 12, extends downwardly over the upper edge of breather duct 10. The lower end of sheath 11 terminates above the normal high water level. The breather tube and sheath may be of any suitable material, such as, for example, hard rubber, plastic, or metal, that will not collapse under the pressure of water under flood conditions.

When the water rises above its normal high level a distance sufficient to cover the lower end of the sheath, which preferably is approximately two inches above the normal high water level, it traps a certain amount of air in the space between the sheath, breather tube and wiring 9, and in the upper portion of the switch housing. This entrapped air cannot escape through the switch housing, and is compressed by the increased pressure of water as the water level rises above the lower end of 3,154,652 Patented Oct. 27, 1964 the sheath. The importance of this increase of pressure of the entrapped air will hereinafter be discussed in connection with the operation of the switch mechanism enclosed in the switch housing 4.

The switch housing 4 comprises an inverted cupshaped member 13 having a top wall 14 and a depending cylindrical wall 15. A diaphragm 16, preferably made of neoprene or some similar material, extends across the bottom of the cylindrical wall and is secured in place by a buffer tube 17. The buffer tube is preferably made of molded rubber, and has a perforated disk 18 to protect the diaphragm. The perforations 19 insure that the pressure of the water is transmitted to the diaphragm and also prevent the disk 18 from interfering with the operation of the diaphragm.

The top wall 14 has an upstanding annular flange 2i) adapted to t tightly within the lower end of breather tube 10. The inner surface of flange 20 is spaced from wiring 9 which extends therethrough to form a passageway 21 permitting air trapped under the sheath 11 and inside the breather tube 10 to flow into the upper portion of housing 13. Under ood conditions, the entrapped air presses against the top of the diaphragm and counterbalances a portion of the pressure against the bottom of the diaphragm and thus limits the strain to which the diaphragm is subjected by the external pressure of the water. The pressure differential on opposite sides of the diaphragm is regulated by the length of the sheath and the volume of air that is trapped above the diaphragm when the water rises high enough -to cover the lower end of the sheath. After the predetermined pressure against the bottom of the diaphragm is attained, any increase in pressure due to continued rise of the water level acts equally on the topi as well as the bottom of the diaphragm.

If the entire room in which the unit is located is flooded,

the liquid level control mechanism is protected by this equalization of excess pressure. The liquid level control will start the pump operating as soon as power can reach the pump control after such flood conditions. This protection against excessive pressure is important because it prevents any impairment of the normal sensitivity of the diaphragm controlled switch.

The cup shaped member 13 has an annular recess 22 in its inner surface, and a metal plate 23 has its peripheral edge secured in said recess. The plate 23 has a few small perforations (not shown) to allow air owing through passageway 21 to exert pressure against the upper surface of the diaphragm 16. The plate 23 also has a centrally disposed aperture through which a tubular non-conducting bushing 24 extends. A brass shaft 25 fitting in the bushing 24 has an enlarged head 26 that fits in an aperture in a ceramic magnet 27. The bottom of the enlarged head 26 is spaced slightly above the bottom of the magnet 27 to provide clearance between the head 26 and the top of plate 23 to prevent a short between the shaft and plate 23. The magnet may be of any suitable shape, but is preferably a flat, annular disk. A plastic insulator 28 is seated on the top of the head 26 to prevent contact between the head 26 of the brass shaft 25 and the end of an adjusting screw 29 threaded in an aperture in an iron detent cap 30.

The iron detent cap Sil rests on the plate 23 and straddles the ceramic magnet 27. The distance between ceramic magnet and the iron detent cap determines the strength of the magnetic field. The screw 29 is threaded through the detent cap 30 to limit the movement of the shaft 25, and the magnet secured thereto, toward the detent cap. The plastic insulator 28 is flush with or slightly below the top of the magnet 27, so that the magnet may move very close to the underside of the 3 top of the detent cap. The screw 29 always projects below the top of the detent cap far enough to prevent the magnet from moving into contact with the detent cap for a reason hereinafter disclosed.

The lower end of the shaft 25 is reduced in diameter to form a tit 31 that is peened to rivet a contactor plate 32 to the end of the shaft. The plate 32, which has two contact buttons 33 projecting upwardly therefrom, is bonded to the diaphragm 16 in any suitable manner,

Two insulators 34 are secured to plate 23 in any suitable manner. One lead from wiring 9 extends through each insulator and is connected to a contact blade 35 supported by the insulator. Each blade 35 extends laterally from its insulator in vertically spaced relationship to the contactor plate 32. A contact button 36 depends from each blade 35 in vertical alignment with the buttons 33. The holding force of the magnet determines the pressure that must be exerted against the diaphragm to close the switch and thereby energize the circuit controlling operation of the pump motor.

When the liquid level in the sump is low and there is no pressure tending to distend the diaphragm, the magnet 27 rests on the plate 23. As the water rises and exerts pressure that is transmitted to the underside of the diaphragm, upward movement of the diaphragm is resisted by a holding force that includes the Weight of the magnet, shaft 25 and plate 32, as well as the magnetic force between the magnet 27 and plate 23. When the water level rises the pressure increases, and when the pressure exceeds this holding force, the central portion of the diaphragm moves the contactor plate 32 upwardly, and the magnet 27 is separated from the plate 23. As the distance of the magnet from the plate 23 increases, the holding field shrinks rapidly, causing an excess of residual energy suicient to close the contacts, spring the contact blades upwardly, and to move the magnet upwardly into contact with the screw 29.

The iield of the iron detention cap has the same strength levels Ias the plate 23, since the same magnet is used for both. If the magnet were permitted to engage the underside of the detention cap, the magnetic force would hold the contactor plate 32 in its upper position ,with the contacts closed, until the water pressure against the diaphragm is completely relieved, and the pump motor would operate continuously after the water level was reduced to the point at which the pump operation is normally stopped. The adjusting screw 29 prevents the magnet from such engagement with the detention cap.

When the contact buttons 33 and 36 are closed, the magnet is moved close to the top of the detention cap and the contact blades 35 are deflected upwardly to some extent. After the water level has been reduced to relieve the diaphragm from the pressure exerted against its underside, the magnetic eld of the iron detention cap is the only force tending to hold rthe contacts closed. The weight of the magnet, shaft and plate 32, together with the tension of the contact blades 35, tend to move the plate 32 downwardly against the magnetic eld of the detention cap. The screw 29 is adjusted to limit the upward movement of the magnet and thus limit the magnetic iield of the iron detention cap to predetermined strength. The strength of the magnetic field of the iron detention cap is so limited that the force exerted by the weight of the magnet, shaft and plate, together with the tension of the contact blades, exceeds the holding force of the eld of the iron detention cap and moves the magnet and contactor plate 32 downwardly when the water reaches the level at which it is desired to stop the pump motor. When the water reaches the desired level, the force urging the magnet and plate 32 downwardly moves the magnet and plate 32 down fast, assisted at the end of the movement by the magnetic field of plate 23, thus minimizing the possibility of contact burn.

Although I have described a preferred embodiment of my invention in considerable detail, it will be understood that the description thereof is intended to be illustrative, rather than restrictive, as many details of the construction may be modied or changed without departing from the spirit or scope of my invention. Accordingly, I do not desire to be restricted to the exact construction described.

I claim:

1. A liquid level control comprising a switch housing mounted in a location in which it is subjected to water of varying depth including a depth sucient to completely immerse said housing, a switch enclosed in said housing, pressure sensitive means in said housing for closing said switch at a predetermined pressure, one surface of said pressure sensitive means being exposed to said water, and mean automatically forming an air buffer between said water and the opposite surface of said pressure sensitive means when said housing is completely immersed in said water `to counteract any pressure against said pressure sensitive means in excess of said predetermined pressure.

2. A liquid level control comprising a switch housing mounted in a location in which it is subjected to water of varying depth including a depth suicient to completely immerse said housing, a switch enclosed in said housing, a pressure sensitive diaphragm in said housing, contact means secured to the upper surface of said diaphragm and movable by said diaphragm into and out of contact with said switch, the underside of said diaphragm being exposed to the pressure of said water, and means for exerting pressure against the upper surface of said diaphragm, when the water rises to a predetermined level, to counteract the force of the water pressure exerted against the underside of said diaphragm in excess of a predetermined maximum.

3. A liquid level control comprising a switch housing mounted in a location in which it is subjected to water of varying depth including a depth sucient to completely immerse said housing, a switch enclosed in said housing, a pressure sensitive diaphragm in said housing below said switch, contact means secured to the upper surface of said diaphragm, the underside of said diaphragm being exposed to pressure of said water, said diaphragm being movable upwardly to carry said contact means into contact with said switch and thereby close said switch upon application of a predetermined pressure to its underside, and means for exerting pressure against the upper surface of said diaphragm to counteract any pressure against the underside of said diaphragm in excess of said predetermined pressure.

4. In a liquid level control, a switch housing mounted in a location in which it is subjected to water of varying depth including a depth suicient to completely immerse said housing, a switch in said housing, a pressure sensitive diaphragm in said housing, contact means secured yto the upper surface of said diaphragm for operating said switch, the underside of said diaphragm being exposed to the pressure of said Water, said switch housing having an opening therethrough above said diaphragm, a breather duct sealing said opening, said breather duct having an open upper end, a sheath forming a closure extending downwardly over the upper end portion of said breather duct in spaced relationship thereto to provide an air passageway between said sheath and said breather duct, the lower end of said sheath terminating above the normal high water level to which said housing is exposed, whereby any rise in the level of the water in which said housing is immersed past the lower end of the sheath will trap air in said breather duct, and an air passageway leading from said breather duct to the upper side of said diaphragm, whereby any increase in the rise of the water level past the lower end of the sheath will increase the pressure against the upper side of the diaphragm to counteract the increased pressure against the underside of .the diaphragm.

5. In a liquid level control, a switch housing, a switch in said housing mounted in a location in which it is subjected to water of varying depth including a depth sufficient to completely immerse said housing, a pressure sensitive diaphragm in said housing, contact means secured to the upper surface of said diaphragm for operating said switch, the underside of said diaphragm being exposed to the pressure of said water, said switch housing having an opening therethrough above said diaphragm, a breather duct sealing said opening, said breather duct having an open upper end, wiring extending from said switch through said opening and said breather duct, the perimeter of said wiring being less than the circumference of said breather duct and said opening to provide an air passageway from the breather duct into the upper portion of said housing, a sheath bonded to said wiring above the upper end of said breather duct, said sheath extending downwardly over the upper end portion of said breather duct in spaced relationship thereto to provide an air passageway between said sheath and said breather duct, the lower end of said sheath terminating above the normal high Water level to which said housing is exposed, whereby any rise in the level of the water in which said housing is immersed past the lower end of the sheath will trap air in said breather duct, and an air passageway leading from said breather duct to the upper side of said diaphragm, whereby any increase in the rise of the water level past the lower end of the sheath will increase the pressure against the upper side of the diaphragm to counteract the increased pressure against the underside of the diaphragm.

6. A liquid level control comprising a housing, a pressure sensitive diaphragm mounted in said housing with its lower surface exposed to water of varying depth, a switch enclosed in said housing above said diaphragm, said switch comprising a contactor plate bonded to the upper surface of said diaphragm and a pair of contacts above said contactor plate, pressure against the underside of said diaphragm being effective to move said contactor plate upwardly to close said switch, a shaft projecting upwardly from said contactor plate, a magnet rigidly secured to said shaft, an iron detention cap mounted above said magnet, upward movement of said diaphragm being effective to move said magnet upwardly toward said iron detention cap to create a magnetic force holding said contactor plate in switch closing position, and adjustable means controlling the distance between the uppermost position of said magnet and said iron detention cap to limit the magnetic force holding said switch in closed position.

7. A liquid level control comprising a housing, a pressure sensitive diaphragm mounted in said housing with i-ts lower surface exposed to water of varying depth, a switch enclosed in said housing above said diaphragm, said switch comprising a contactor plate bonded to the upper surface of said diaphragm and a pair of contacts above said contactor plate, pressure against the underside of said diaphragm being effective to move said contactor plate upwardly to close said switch, a shaft projecting upwardly from said contactor plate, a magnet rigidly secured to said shaft, an iron detention cap mounted above said magnet, upward movement of said diaphragm being effective to move said magnet upwardly toward said iron detention cap to create a magnetic force holding said contactor plate in switch closing position, adjustable means controlling the distance between the uppermost position of said magnet and said iron detention cap to limit the magnetic force holding said switch in closed position, and means for counteracting pressure in excess of a predetermined pressure exerted against the underside of said diaphragm.

8. A liquid level control comprising a housing, a pressure sensitive diaphragm mounted in said housing with its lower surface exposed to water of varying depth, a switch enclosed in said housing above said diaphragm, said switch comprising a contactor plate bonded to the upper surface of said diaphragm and a pair of contacts above said contactor plate, pressure against the underside of said diaphragm being effective to move said contactor plate upwardly to close said switch, a shaft projecting upwardly from said contactor plate, a magnet rigidly secured to said shaft, an iron detention cap mounted above said magnet, upward movement of said diaphragm being effective to move said magnet upwardly toward said iron detention cap to create a magnetic force holding said contactor plate in Switch closing position, and means for trapping air above said diaphragm when the water rises over a predetermined level to counteract any additional pressure exerted against the underside of said diaphragm.

References Cited by the Examiner UNITED STATES PATENTS 2,275,556 3/ 46 Rasmussen 200-83 2,481,612 9/ 49 Nicholson 200--81 2,566,704 9/51 Leibing 200-83 2,922,854 l/ Neilsen 20G-83 3,042,771 7/ 62 Oliveau 200-81 BERNARD A. GILHEANY, Primary Examiner. MAX L. LEVY, Examiner. 

1. A LIQUID LEVEL CONTROL COMPRISING A SWITCH HOUSING MOUNTED IN A LOCATION IN WHICH IT IS SUBJECTED TO WATER OF VARYING DEPTH INCLUDING A DEPTH SUFFICIENT TO COMPLETELY IMMERSE SAID HOUSING, A SWITCH ENCLOSED IN SAID HOUSING, PRESSURE SENSITIVE MEANS IN SAID HOUSING FOR CLOSING SAID SWITCH AT A PREDETERMINED PRESSURE, ONE SURFACE OF SAID PRESSURE SENSITIVE MEANS BEING EXPOSED TO SAID WATER, AND MEAN AUTOMATICALLY FORMING AN AIR BUFFER BETWEEN SAID WATER AND THE OPPOSITE SURFACE OF SAID PRESSURE SENSITIVE MEANS WHEN SAID HOUSING IS COMPLETELY IMMERSED IN SAID WATER TO COUNTERACT ANY PRESSURE AGAINST SAID PRESSURE SENSITIVE MEANS IN EXCESS OF SAID PREDETERMINED PRESSURE. 